Liquid phase oxidation of halogenated ortho-xylenes

ABSTRACT

A method for the manufacture of halophthalic acid by liquid phase oxidation of halo-ortho-xylene is disclosed. The halophthalic acid may be dehydrated to form halophthalic anhydride which is useful in the synthesis of polyetherimide.

BACKGROUND OF INVENTION

[0001] This invention relates to liquid phase oxidation of halogensubstituted alkyl aromatic compounds. In particular, the inventionrelates to liquid phase oxidation of halo-ortho-xylene to producehalophthalic acid which can be dehydrated to produce halophthalicanhydride.

[0002] Liquid phase oxidation has long been used to produce dicarboxylicacids from dialkyl benzenes. Of particular interest has been theoxidation of dimethyl benzene (xylene) to phthalic acid, especially theoxidation of para-xylene to terephthalic acid, which is used in theproduction of polybutylene terephthalate. The liquid phase oxidation ofxylene to phthalic acid requires the use of a catalyst, typically acobalt/manganese/bromine catalyst system, and is generally performed ina carboxylic acid solvent such as acetic acid. The catalyst system maybe augmented by the use of a co-catalyst such as zirconium, hafnium orcerium. Phthalic acid is an easily isolable solid, which can be filteredout of the reaction mixture.

[0003] Liquid phase oxidation, using a cobalt/manganese/bromine catalystsystem and a carboxylic acid solvent, has also been applied tohalogenated xylene with some success. The oxidation of the halogenatedxylene is more difficult than the oxidation of xylene due to presence ofa halogen, which is an electron withdrawing substituent, on the benzenering. The greater difficulty in oxidation results in a lower reactionselectivity and a larger amount of partial oxidation and side productsthan seen in the liquid phase oxidation of xylene under similarconditions. Additionally, halogenated phthalic acid is difficult toseparate from the partial oxidation and side products, even bydistillation. Thus it is clear that in order for a method of liquidphase oxidation of halogenated xylene to be commercially successful thereaction yield and the reaction selectivity must be very high.Optimally, for a useful commercial process, the reaction selectivityshould be high enough to result in only negligible amounts of partialoxidation and side products thus removing the need for isolation ofhalophthalic acid.

SUMMARY OF INVENTION

[0004] A method for the manufacture of halophthalic acid comprisesforming a reaction mixture comprising a mixture of about 7 to about 3parts by weight of acetic acid to 1 part by weight of ahalo-ortho-xylene, about 0.25 to about 2 mole percent, based on thehalo-ortho-xylene, of a cobalt source, about 0.1 to about 1 molepercent, based on the halo-ortho-xylene, of a manganese source, about0.01 to about 0.1 mole percent, based on the halo-ortho-xylene, of asource of a metal selected from zirconium, hafnium and mixtures thereof,and about 0.02 to about 0.1 mole percent, based on thehalo-ortho-xylene, of a bromide source; maintaining the reaction mixtureat a pressure of at least about 1600 kilopascals (Kpa) and at atemperature of about 130° C. to about 200° C.; introducing a molecularoxygen containing gas to the reaction mixture at a rate of at leastabout 0.5 normal m³ of gas/hour per kilogram (kg) of halo-ortho-xylenein the reaction mixture for a time sufficient to provide at least about90 percent conversion of the halo-ortho-xylene to halophthalic acid.

[0005] In another embodiment, a method for the manufacture ofhalophthalic anhydride comprises forming a reaction mixture comprising amixture of about 7 to about 3 parts by weight of acetic acid to 1 partby weight of a halo-ortho-xylene, about 0.25 to about 2 mole percent,based on said halo-ortho-xylene, of a cobalt source, about 0.1 to about1 mole percent, based on said halo-ortho-xylene, of a manganese source,about 0.01 to about 0.1 mole percent, based on said halo-ortho-xylene,of a source of a metal selected from zirconium, hafnium and mixturesthereof, and about 0.02 to about 0.1 mole percent, based on saidhalo-ortho-xylene, of a bromide source; maintaining said reactionmixture at a pressure of at least about 1600 Kpa and at a temperature ofabout 130° C. to about 200° C.; introducing a molecular oxygencontaining gas to the reaction mixture at a rate of at least about 0.5normal m³ of gas/kg of halo-ortho-xylene for a time sufficient toprovide at least about 90 percent conversion of said halo-ortho-xyleneto halophthalic acid with less than about 600 parts per million (ppm) ofhalophthalide; removing the acetic acid and any water formed as a resultof the reaction by distillation; and dehydrating the halophthalic acidto form halophthalic anhydride.

[0006] In another aspect, the method for the manufacture of halophthalicacid comprises forming a reaction mixture comprising a mixture of about7 to about 3 parts by weight of acetic acid to 1 part by weight of ahalo-ortho-xylene, about 0.8 to about 1.2 mole percent, based on thehalo-ortho-xylene, of a cobalt source, about 0.4 to about 0.6 molepercent, based on the halo-ortho-xylene, of a manganese source, about0.04 to about 0.06 mole percent, based on the halo-ortho-xylene, of asource of a metal selected from zirconium, hafnium and mixtures thereof,and less than about 0.04 mole percent, based on the halo-ortho-xylene,of a source of bromide; maintaining the reaction mixture at a pressureof at least about 1600 Kpa and at a temperature of about 130° C. toabout 200° C.; introducing a molecular oxygen containing gas to thereaction mixture at a rate of at least about 0.5 normal m³ of gas/kg ofhalo-ortho-xylene for a time sufficient to provide at least about 90percent conversion of said halo-ortho-xylene to halophthalic acid.

[0007] In another aspect, a method for the manufacture of halophthalicanhydride comprises forming a reaction mixture comprising a mixture ofabout 7 to about 3 parts by weight of acetic acid to 1 part by weight ofa halo-ortho-xylene, about 0.8 to about 1.2 mole percent, based on saidhalo-ortho-xylene, of cobalt acetate or cobalt acetate hydrate, about0.4 to about 0.6 mole percent, based on said halo-ortho-xylene, ofmanganese acetate or manganese acetate hydrate, about 0.04 to about 0.06mole percent, based on said halo-ortho-xylene, of zirconium acetate orzirconium acetate hydrate, less than about 0.04 mole percent, based onsaid halo-ortho-xylene, of sodium bromide; maintaining said reactionmixture at a pressure of at least about 1600 Kpa and at a temperature ofabout 130° C. to about 200° C.; introducing a molecular oxygencontaining gas to said reaction mixture at a rate of at least about 0.5normal m³ of gas/kg of halo-ortho-xylene in the reaction mixture for atime sufficient to provide at least about 90 percent conversion of saidhalo-ortho-xylene to halophthalic acid; removing the acetic acid and anywater formed as a result of the reaction by distillation; separating thewater from the acetic acid and recycling the acetic acid; anddehydrating the halophthalic acid to form halophthalic anhydride.

[0008] In another embodiment, a method for the manufacture ofpolyetherimide comprises forming a reaction mixture comprising a mixtureof about 7 to about 3 parts by weight of acetic acid to 1 part by weightof a halo-ortho-xylene, about 0.25 to about 2 mole percent, based on thehalo-ortho-xylene, of a cobalt source, about 0.1 to about 1 molepercent, based on the halo-ortho-xylene, of a manganese source, about0.01 to about 0.1 mole percent, based on the halo-ortho-xylene, of asource of a metal selected from zirconium, hafnium and mixtures thereof,about 0.02 to about 0.1 mole percent, based on the halo-ortho-xylene, ofa bromide source; maintaining the reaction mixture at a pressure of atleast about 1600 KPa and at a temperature of about 130° C. to about 200°C.; introducing a molecular oxygen containing gas to the reactionmixture at a rate of at least about 0.5 normal m³ of gas/kg ofhalo-ortho-xylene for a time sufficient to provide at least about 90percent conversion of the halo-ortho-xylene to halophthalic acid withless than about 600 parts per million (ppm) of halophthalide; removingthe acetic acid and any water formed as a result of the reaction bydistillation; dehydrating the halophthalic acid to form halophthalicanhydride; reacting the halophthalic anhydride with 1,3-diaminobenzeneto form bis (halophthalimide) (II)

[0009] wherein X is a halogen; and reacting bis(halophthalimide) (II)with an alkali metal salt of a dihydroxy substituted aromatichydrocarbon having the formula (IV)

OH—A²OH  (IV)

[0010] wherein A² is a divalent aromatic hydrocarbon radical to form thepolyetherimide.

DETAILED DESCRIPTION

[0011] A method for the manufacture of halophthalic acid comprisesforming a reaction mixture comprising a mixture of about 7 to about 3parts by weight of acetic acid to 1 part by weight of ahalo-ortho-xylene, about 0.25 to about 2 mole percent, based on thehalo-ortho-xylene, of a cobalt source, about 0.1 to about 1 molepercent, based on the halo-ortho-xylene, of a manganese source, about0.01 to about 0.1 mole percent, based on the halo-ortho-xylene, of asource of a metal selected from zirconium, hafnium and mixtures thereof,and about 0.02 to about 0.1 mole percent, based on thehalo-ortho-xylene, of a bromide source. The reaction mixture ismaintained at a pressure of at least about 1600 Kpa and at a temperatureof about 130° C. to about 200° C. A molecular oxygen containing gas isintroduced to the reaction mixture at a rate of at least about 0.5normal m³ of oxygen containing gas/hour per kg of halo-ortho-xylene inthe reaction mixture for a time sufficient to provide at least about 90percent conversion of the halo-ortho-xylene to halophthalic acid. Theintroduction of the molecular oxygen containing gas creates an oxygencontaining off gas, which preferably has an oxygen concentration of lessthan about 3 percent by volume of the off gas.

[0012] Using the method for manufacture of halophthalic acid andanhydride described herein, the high yield synthesis of high purityhalophthalic acid and anhydride is possible on a scale employinghundreds of kilograms of halo-ortho-xylene by liquid phase oxidation inthe presence of about 0.25 to about 2 mole percent (mol %) of a cobaltsource, about 0.1 to about 1 mol % of a manganese source, about 0.01 toabout 0.1 mol % of a source of a metal selected from zirconium, hafniumand mixtures thereof, and about 0.02 to about 0.1 mol % of a bromidesource. Applicants have discovered that in large scale liquid phaseoxidations employing halo-ortho-xylene the amount of bromide can have asignificant impact on the amount of impurities present in the finalproduct. The use of decreasing molar percentages of bromide result in aproduct, either halophthalic acid or anhydride, with a decreased levelof impurities such as halophthalide. While the reasons for thisphenomenon are not clearly understood it is contemplated that even lowerlevels of bromide, molar percentages less than about 0.02, may be usefulin producing high purity halophthalic acid or anhydride in even largerscale liquid phase oxidations such as those employing thousands ofkilograms of halo-ortho-xylene.

[0013] Halo-ortho-xylene suitable for use in the oxidation has thestructure (IV)

[0014] wherein X is halogen. Preferably X is chlorine. The halogensubstituent may be in the 3 position (the 3-isomer) or in the 4 position(the 4-isomer). The halo-ortho-xylene used in the liquid-phase oxidationmay also be a mixture of the 3-isomer and the 4-isomer.

[0015] The liquid phase oxidation preferably employs acetic acid as asolvent although other lower carboxylic acids may be employed, asreadily appreciated by one of ordinary skill in the art. In general,acetic acid with a water content of up to about 3 percent may beemployed. Typically the acetic acid is present in an amount of 7 to 3parts by weight to 1 part by weight of halo-ortho-xylene. Preferably theacetic acid is present in an amount of 5 to 3 parts by weight to 1 partby weight of halo-ortho-xylene.

[0016] Suitable molecular oxygen containing gases include gases orcombinations of gases which are a source of molecular oxygen (O₂), forexample, 100% oxygen and mixtures of oxygen with inert gas with asufficient concentration of oxygen to effect oxidation. Sufficientoxygen concentrations typically are greater than or equal to about 6%oxygen, preferably greater than or equal to about 15%, more preferablygreater than or equal to about 20%. Clearly mixtures with greater thanor equal to about 50% oxygen may also be used. As will be appreciated byone of skill in the art, the concentration of oxygen may affect the rateof the reaction. A preferred molecular oxygen containing gas is air.

[0017] Useful cobalt, manganese, bromine, zirconium, and hafnium sourcesare those sources which are soluble in acetic acid. As to the cobalt,manganese, zirconium or hafnium sources these include the metalsthemselves or any of their salts, complexes or compounds. These include,but are not limited to, acetates, citrates, stearates, napthenates,acetylacetonates, benzoylacetonates, carbonates, sulfates, bromides,chlorides, fluorides, nitrates, hydroxides, alkoxides, nitrides,triflates, hydrates of the foregoing and mixtures of the foregoing.Preferably the cobalt in the cobalt source is in a +2 or +3 oxidationstate. Preferably the manganese in the manganese source is in a +2 or +3oxidation state. Examples of bromide sources include, but are notlimited to, bromine, hydrogen bromide, a metal-bromide salt such assodium bromide and organic bromides. Examples of organic bromidesinclude tetrabromoethane, ethyl bromide, ethylene bromide, bromoform,xylyl bromide, xylylene bromide and mixtures comprising at least one ofthe organic bromides.

[0018] The mole percent (mol %) of the cobalt, manganese, zirconium,hafnium, and bromine are based on the amount of halo-ortho-xylenepresent at the beginning of the reaction. The cobalt source is generallypresent in amounts of about 0.25 to about 2 mol %. Preferably, thecobalt source is present in an amount of less than about 1.2 mol %. Inaddition, it is also preferable for the cobalt source to be present inan amount greater than or equal to about 0.5 mol %, and more preferablyin an amount greater than or equal to about 0.8 mol %. It isparticularly preferred for the amount of the cobalt source to be about 1mol %.

[0019] The manganese source is present in amounts of about 0.1 to about1 mol %. Preferably, the manganese source is present in an amount ofless than or equal to about 0.6 mol %. Additionally, it is alsopreferable for the manganese source to be present in an amount greaterthan or equal to about 0.3 mol %, more preferably greater than or equalto about 0.4 mol %. In a particularly preferred embodiment, themanganese source is present in an amount of about 0.5 mol %.

[0020] The bromide source is generally present in amounts of about 0.02to about 0.1 mol %. Preferably, the amount of the bromide source is lessthan or equal to 0.8 mol %, more preferably less than or equal to about0.5 mol %, even more preferably less than or equal to 0.4 mol %, andmost preferably less than or equal to 0.3 mol %.

[0021] The zirconium source, hafnium source or mixture thereof isgenerally present in amounts of about 0.01 to about 0.1 mol %.Preferably, the zirconium source, hafnium source or mixture thereof ispresent in an amount less than or equal to about 0.06 mol %.Additionally it is also preferable for, the zirconium source, hafniumsource or mixture thereof to be present in an amount greater than orequal to about 0.03 mol %, more preferably greater than 0.04 mol %. In aparticularly preferred embodiment, the zirconium source, hafnium sourceor mixture thereof is present in an amount of about 0.05 mol %.

[0022] In an exemplary process, the halophthalic acid may be produced bycombining halo-ortho-xylene; the cobalt source; the manganese source;the bromine source; and the zirconium source, hafnium source or mixturethereof, in acetic acid in a reaction vessel. The reaction vessel isestablished at a pressure of greater than about 1600 Kpa at the desiredtemperature. The temperature of the reaction is typically about 130° C.to about 200° C., preferably about 150° C. to about 170° C., and morepreferably greater than about 160° C. The molecular oxygen containinggas is then introduced. The flow of the molecular oxygen containing gascreates an oxygen containing off gas that preferably has an oxygenconcentration of less than 3% by volume, preferably less than about 1%by volume. The oxygen concentration of the off gas may be determined byparamagnetic transduction oxygen analysis or other method known in theart. Useful flow rates are typically greater than or equal to 0.5 normalcubic meter (m³)/hour per kilogram (kg) of halo-ortho-xylene andpreferably greater than or equal to 1.0 normal cubic meter (m³)/hour perkilogram (kg) of halo-ortho-xylene. A normal cubic meter is defined ascubic meter under standard temperature and pressure condition.Preferably the reaction mixture is agitated using standard methods suchas mechanical stirring. The flow of molecular oxygen containing gas iscontinued until at least about 90% of halo-ortho-xylene has beenconverted to halophthalic acid, preferably until greater than 95% hasbeen converted. The amount of conversion achieved in the reaction canreadily be determined through the use of gas chromatography, massspectrometry or other methods known in the art. In our experience,amount of time required to reach 90% conversion of halo-ortho-xylene isabout 3 to about 6 hours.

[0023] Additionally, the method to manufacture halophthalic acid oranhydride may include the optional step of monitoring the oxygenconcentration of the off gas. When the oxygen concentration of the offgas exceeds about 3% by volume that signals a slowing of the reaction.Once the oxygen concentration of the off gas exceeds about 3% by volumethe flow of the molecular oxygen containing gas may be modified so as tomaintain the oxygen concentration of the off gas below about 5% byvolume. The flow of the molecular oxygen containing gas may be modifiedin several ways. The molecular oxygen containing gas may be diluted withan inert gas so as to decrease the oxygen concentration in the molecularoxygen containing gas, the flow rate of the molecular oxygen containinggas may be decreased, the source of the molecular oxygen containing gasmay be changed so as to employ a molecular oxygen containing gas with alower oxygen concentration or these methods may be combined so as tomaintain the oxygen concentration of the off gas below about 5% byvolume. The modified flow of molecular oxygen containing gas may then becontinued until at least about 90% of halo-ortho-xylene has beenconverted to halophthalic acid, preferably until greater than 95% hasbeen converted. The amount of conversion achieved in the reaction canreadily be determined through the use of gas chromatography, massspectrometry or other methods known in the art.

[0024] After the reaction reaches the desired level of completion, thehalophthalic acid may be recovered as halophthalic acid or halophthalicanhydride. Many applications such as pharmaceutical applications andpolymer synthesis require halophthalic acid and halophthalic anhydridewith a high degree of purity. Such high degree of purity may be achievedby the method described herein. In fact, halophthalic acid andhalophthalic anhydride containing less than about 600 ppm ofhalophthalide, preferably less than about 500 ppm of halophthalide, andmore preferably less than about 400 ppm of halophthalide is readilyachievable. Additionally, chlorophthalic acid and chlorophthalicanhydride containing less than about 1% by weight of phthalic anhydrideand chlorobenzoic acid may also be achieved. Chlorotoluic acids anddichlorophthalic acids are typically not detected.

[0025] Most of the acetic acid as well as water produced in the reactioncan be removed by distillation at approximately atmospheric pressure,typically by heating to about 200° C. at 200 Kpa. The acetic acid andwater are removed as a vapor and condensed. The water may then beremoved from the acetic acid and the acetic acid may be recycled. Somedehydration of the halophthalic acid to form halophthalic anhydride mayoccur simultaneously with the removal of acetic acid and water.Furthermore, the removal of acetic acid and water may be combined withdehydration to form a single step. Dehydration is typically donethermally by distillation under vacuum at an elevated temperatureallowing dehydration and isolation of the halophthalic anhydride fromany remaining acetic acid and water to occur simultaneously. Dehydrationmay also be carried out by other chemical reactions well known to thoseskilled in the art such as treatment with acetic anhydride. Afterdistillation the halophthalic anhydride is typically greater than about95 percent, preferably greater than about 97 percent, and mostpreferably greater than about 99 percent pure. Halophthalic anhydridesof high purity are used in the synthesis of polyetherimide, a high heatengineering plastic.

[0026] Polyetherimides are high heat engineering plastics having avariety of uses. One route for the synthesis of polyetherimides proceedsthrough a bis(4-halophthalimide) having the following structure (I):

[0027] wherein Y is a divalent alkylene, cycloalkylene, or arylenemoiety and X is a halogen. The bis(4-halophthalimide) wherein Y is a1,3-phenyl group (II) is particularly useful.

[0028] Bis(halophthalimide)s (I) and (II) are typically formed by thecondensation of amines, e.g., 1,3-diaminobenzene with anhydrides, e.g.,4-halophthalic anhydride

[0029] Polyetherimides may be synthesized by the reaction of thebis(halophthalimide) with an alkali metal salt of a dihydroxysubstituted aromatic hydrocarbon in the presence or absence of phasetransfer catalyst. Suitable phase transfer catalysts are disclosed inU.S. Pat. No. 5,229,482, which is herein incorporated by reference.

[0030] Suitable dihydroxy substituted aromatic hydrocarbons includethose having the formula (IV)

OH—A²OH  (IV)

[0031] wherein A² is a divalent aromatic hydrocarbon radical. SuitableA² radicals include m-phenylene, p-phenylene, 4,4′-biphenylene,4,4′-bi(3,5-dimethyl)phenylene, 2,3-bis(4-phenylene)propane and similarradicals such as those disclosed by name or formula in U.S. Pat. No.4,217,438.

[0032] The A² radical preferably has the formula (V)

—A³—Q—A⁴—  (V)

[0033] wherein each of A³ and A⁴ is a monocyclic divalent aromatichydrocarbon radical and Q is a bridging hydrocarbon radical in which oneor two atoms separate A³ from A⁴. The free valence bonds in formula (V)are usually in the meta or para positions of A³ and A⁴ in relation to Y.A³ and A⁴ may be substituted phenylene or hydrocarbon-substitutedderivative thereof, illustrative substituents (one or more) being alkyland alkenyl. Unsubstituted phenylene radicals are preferred. Both A³ andA⁴ are preferably p-phenylene, although both may be o- or m-phenylene orone o- or m-phenylene and the other p-phenylene.

[0034] The bridging radical, Q, is one in which one or two atoms,preferably one, separate A³ from A⁴. Illustrative radicals of this typeare methylene, cyclohexylmethylene, 2-(2,2,1)-bicycloheptylmethylene,ethylene, isopropylidene, neopentylidene, cyclohexylidene, andadamantylidene. The preferred radical of formula (IV) is2,2-bis(4-phenylene)propane radical which is derived from bisphenol Aand in which Q is isopropylidene and A³ and A⁴ are each p-phenylene.

[0035] It is clear to one of ordinary skill in the art that anyimpurities present in the halophthalic anhydride will be carried throughto subsequent steps in the polyetherimide synthesis. The presence ofsignificant levels of impurities in subsequent steps can interfere withpolymerization and cause discoloration of the final product,polyetherimide.

[0036] All patents cited are herein incorporated by reference.

[0037] The invention is further illustrated by the followingnon-limiting examples.

EXAMPLES 1-5

[0038] In a laboratory scale reactor 492 grams (g) (3.5 mol) ofchloro-ortho-xylene (a mixture of about 30% 3-chloro-ortho-xylene andabout 70% 4-chloro-ortho-xylene), 1925 g of glacial acetic acid, 8.7 g(1 mol %) of cobalt acetate tetrahydrate, 4.3 g (0.5 mol %) of manganeseacetate tetrahydrate, 1.0 g (0.06 mol %) zirconium acetate solution, 4.3g (1.5 mol %) sodium acetate and varying amounts of sodium bromide werecombined. The reactor was filled with nitrogen, pressurized to 1900 KPaand heated to about 160° C. Air was then introduced to the reactorthrough a dip tube. Initially, the off gas oxygen concentration wasgreater than 0 but less than 1 percent. The reaction mixture wasagitated throughout the reaction time. After about 3 hours the oxygenconcentration of the off gas increased to greater than 3 percent. Theflow of air was stopped. Air diluted with nitrogen so as to have an offgas oxygen concentration of about 5 percent was introduced to thereactor and the temperature of the reactor was increased to about 190°C. The flow of diluted air continued for about 1 to 3 hours.Chlorophthalic acid was determined to be present in an amount of 25 wt %based on the total weight of the reaction mixture. The majority of waterformed by the reaction and the acetic acid were removed underatmospheric distillation. The chlorophthalic acid was dehydrated and anyresidual water and acetic acid were removed under heat and reducedpressure to form chlorophthalic anhydride. Chlorophthalic anhydride wasseparated from the catalyst by distillation under vacuum at distillationtemperatures near 170° C. The isolated chlorophthalic acid was analyzedby gas chromatography. Results are shown in Table 1. TABLE 1 Amount ofChlorophthalides produced Example NaBr mol % wt % ppm 1 * 1.0 0.57 57002 * 0.29 0.25 2500 3 * 0.14 0.01 100 4 0.03 0.46 4600 5 * 0.014 2.3523500

[0039] As can be seen by examples 1-5, chlorophthalic anhydride withvery small amounts of chlorophthalide may be produced on a laboratoryscale, however the amount of bromide required is greater than 0.05 mol%.

EXAMPLES 6-10

[0040] In a pilot scale reaction 200 kilograms (kg) ofchloro-ortho-xylene (a mixture of 3-chloro-ortho-xylene and4-chloro-ortho-xylene), 780 kg of acetic acid, 3.5 kg (1.0 mol %) cobaltacetate tetrahydrate, 1.75 kg (0.5 mol %) manganese acetatetetrahydrate, 0.4 kg (0.05 mol %) zirconium acetate solution, 1.75 kg(1.5 mol %) sodium acetate and varying amounts of sodium bromide werecombined. The amount of sodium bromide was varied by example as shown inTable 2. The reactor was filled with nitrogen, pressurized to 1900 Kpaand heated to about 160° C. Air was introduced to the reactor through adip tube at a flow rate gradually increasing to 200 normal m³ /h.Initially, the off gas oxygen concentration was greater than 0 but lessthan 1 percent. The reaction mixture was agitated throughout thereaction time. After about 1 hour, the reaction temperature wasincreased to 175° C. After about 3 hours the off gas oxygenconcentration increased to greater than 3 percent. The air flow wasstopped. Air diluted with nitrogen so as to have an off gas oxygenconcentration of about 5 percent was introduced into the reactor and thetemperature of the reactor was increased to 190° C. The flow of dilutedair was continued for about 3 hours. Final weight of the reactorcontents was consistent with high conversions of chloro-o-xylene basedon the absorption of 3 moles of 0₂ to generate the diacid and two molesof water. The majority of water formed by the reaction and the aceticacid were removed under atmospheric distillation. The chlorophthalicacid was dehydrated and any residual water and acetic acid were removedunder heat and reduced pressure to form chlorophthalic anhydride.Chlorophthalic anhydride was separated from the catalyst by distillationunder vacuum at distillation temperatures near 170° C. The isolatedchlorophthalic acid was analyzed by gas chromatography. Results areshown in Table 2. TABLE 2 Amount of Chlorophthalides NaBr producedExample mol % (wt %) ppm 6 * 1.02 5.4 54000 7 * 0.14 0.24 2400 8 * 0.100.12 1200 9 0.03 0.02 200 10 0.02 0.03 300

[0041] As can be seen in the preceding examples it is possible toproduce chlorophthalic anhydride with very low levels of chlorophthalidein reactions on a large scale. The overall purity of the chlorophthalicacid produced in Examples 9 and 10 was greater than 98%.

EXAMPLE 11

[0042] In a laboratory scale reactor 40 grams (g) (284 millimole (mmol))of chloro-ortho-xylene (a mixture of about 30% 3-chloro-ortho-xylene andabout 70% 4-chloro-ortho-xylene), 160 g of glacial acetic acid, 567milligrams (mg) (0.8 mol %) of cobalt acetate tetrahydrate, 349 mg (0.5mol %) of manganese acetate tetrahydrate, 9.1 mg (0.06 mol %) zirconiumacetate solution, and 91 mg of 30% solution by weight of hydrogenbromide in acetic acid were combined. The reactor was filled withnitrogen, pressurized to 1900 KPa and heated to about 160° C. Air wasthen introduced to the reactor through a dip tube. Initially, the offgas oxygen concentration was greater than 0 but less than 1 percent. Thereaction mixture was agitated throughout the reaction time. After 1 hourat 160° C. the temperature was increased to about 175° C. After about 3hours the oxygen concentration of the off gas increased to greater than3 percent. The flow of air was stopped. Air diluted with nitrogen so asto have an off gas oxygen concentration of about 5 percent wasintroduced to the reactor and the temperature of the reactor wasincreased to about 190° C. The flow of diluted air continued for about 1to 3 hours. The reaction mixture was analyzed by liquid chromatography(LC) and it was found that the chlorophthalic acid was formed with yieldand impurity levels comparable to the results of Example 2. Using themethod for manufacture of halophthalic acid and anhydride describedherein, the high yield synthesis of high purity halophthalic acid andanhydride is possible on a large scale employing hundreds of kilogramsof halo-ortho-xylene by liquid phase oxidation in the presence of about0.25 to about 2 mol % of a cobalt source, about 0.1 to about 1 mol % ofa manganese source, about 0.01 to about 0.1 mol % of a source of a metalselected from zirconium, hafnium and mixtures thereof, and about 0.02 toabout 0.1 mol % of a bromide source. Applicants have discovered that inlarge scale liquid phase oxidations employing halo-ortho-xylene theamount of bromide can have a significant impact on the amount ofimpurities present in the final product. The use of decreasing molarpercentages of bromide result in either halophthalic acid or anhydridewith a decreased level of impurities such as halophthalide. While thereasons for this phenomenon are not clearly understood it iscontemplated that even lower levels of bromide, molar percentages lessthan about 0.02, may be useful in producing high purity halophthalicacid or anhydride in even larger scale liquid phase oxidations such asthose employing thousands of kilograms of halo-ortho-xylene.

[0043] While the invention has been described with reference to apreferred embodiment, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing fromessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A method for the manufacture of halophthalic acid comprising: forminga reaction mixture comprising: a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.25 to about 2 mole percent, based on said halo-ortho-xylene, of acobalt source, about 0.1 to about 1 mole percent, based on saidhalo-ortho-xylene, of a manganese source, about 0.01 to about 0.1 molepercent, based on said halo-ortho-xylene, of a source of a metalselected from zirconium, hafnium and mixtures thereof, about 0.02 toabout 0.1 mole percent, based on said halo-ortho-xylene, of a source ofbromide; maintaining said reaction mixture at a pressure of at leastabout 1600 Kpa and at a temperature of about 130° C. to about 200° C.;introducing a molecular oxygen containing gas to said reaction mixtureat a rate of at least about 0.5 normal m³ of gas/kg of halo-ortho-xylenein said reaction mixture for a time sufficient to provide at least about90 percent conversion of said halo-ortho-xylene to halophthalic acid. 2.The method of claim 1, wherein the molecular oxygen containing gas hasan oxygen concentration of greater than or equal to about 6% oxygen. 3.The method of claim 1, wherein the molecular oxygen containing gas isair.
 4. The method of claim 1, wherein the cobalt source, manganesesource, zirconium or hafnium source, and bromide source are soluble inacetic acid.
 5. The method of claim 4, wherein the cobalt sourcecomprises cobalt acetate, cobalt napthenate, cobalt sulfate, cobaltacetylacetonate, cobalt benzoylacetonate, cobalt bromide, cobaltcarbonate, cobalt chloride, cobalt fluoride, cobalt nitrate, cobaltstearate, or a hydrate of one of the foregoing cobalt compounds.
 6. Themethod of claim 5, wherein the cobalt source comprises cobalt acetate ora hydrate of cobalt acetate.
 7. The method of claim 4, wherein themanganese source comprises manganese acetate, manganese sulfate,manganese acetylacetonate, manganese bromide, manganese carbonate,manganese chloride, manganese fluoride, or manganese nitrate, or ahydrate of one of the foregoing manganese compounds.
 8. The method ofclaim 7, wherein the manganese source comprises manganese acetate or ahydrate of manganese acetate.
 9. The method of claim 4, wherein thezirconium source comprises zirconium acetate, zirconium sulfate,zirconium citrate, zirconium fluoride, zirconium hydroxide, zirconiumalkoxide, zirconium chloride, zirconium bromide, zirconiumacetylacetonate, or a hydrate of one of the foregoing zirconiumcompounds.
 10. The method of claim 9, wherein the zirconium sourcecomprises zirconium acetate or a hydrate of zirconium acetate.
 11. Themethod of claim 4, wherein the source of hafnium comprises hafniumchloride, hafnium bromide, hafnium fluoride, hafnium iodide, hafniumnitride, hafnium sulfate, hafnium triflate, hafnium nitrate, or ahydrate of one of the foregoing hafnium compounds.
 12. The method ofClaim 11, wherein the source of hafnium comprises hafnium chloride. 13.The method of claim 4, wherein the bromide source comprises bromine,hydrogen bromide, a metal-bromide salt or an organic bromide.
 14. Themethod of claim 13, wherein the bromide source comprises sodium bromide.15. The method of claim 13, wherein the bromide source compriseshydrogen bromide.
 16. The method of claim 1, wherein the amount of thecobalt source is about 0.5 to about 1.2 mole percent, based on saidchloro-ortho-xylene.
 17. The method of claim 1, wherein the amount ofthe manganese source is about 0.3 to about 0.6 mole percent, based onsaid chloro-ortho-xylene.
 18. The method of claim 1, wherein the amountof the source of zirconium or hafnium is about 0.03 to about 0.06 molepercent, based on said chloro-ortho-xylene.
 19. The method of claim 1,wherein the amount of the source of bromide is less than or equal toabout 0.04 mole percent, based on said chloro-ortho-xylene.
 20. Themethod of claim 1, wherein the temperature is greater than or equal to160° C.
 21. The method of claim 1, wherein the conversion of saidchloro-ortho-xylene to chlorophthalic acid is 95 percent or greater. 22.The method of claim 1, wherein said chloro-ortho-xylene comprises the3-isomer, the 4-isomer or a mixture of 3- and 4-isomers.
 23. A methodfor the manufacture of halophthalic anhydride comprising: forming areaction mixture comprising: a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.25 to about 2 mole percent, based on said halo-ortho-xylene, of acobalt source, about 0.1 to about 1 mole percent, based on saidhalo-ortho-xylene, of a manganese source, about 0.01 to about 0.1 molepercent, based on said halo-ortho-xylene, of a source of a metalselected from zirconium, hafnium and mixtures thereof, about 0.02 toabout 0.1 mole percent, based on said halo-ortho-xylene, of a bromidesource; maintaining said reaction mixture at a pressure of at leastabout 1600 Kpa and at a temperature of about 130° C. to about 200° C.;introducing a molecular oxygen containing gas to said reaction mixtureat a rate of at least about 0.5 normal m³ of gas/kg of halo-ortho-xylenein said reaction mixture for a time sufficient to provide at least about90 percent conversion of said halo-ortho-xylene to halophthalic acidwith less than about 600 parts per million (ppm) of halophthalide;removing said acetic acid and any water formed as a result of thereaction by distillation; dehydrating said halophthalic acid to formhalophthalic anhydride.
 24. The method of claim 23, wherein themolecular oxygen containing gas has an oxygen concentration of greaterthan or equal to about 6 percent oxygen.
 25. The method of claim 23,wherein the molecular oxygen containing gas is air.
 26. The method ofclaim 23, wherein the cobalt source, manganese source, zirconium orhafnium source and bromide source are soluble in acetic acid.
 27. Themethod of claim 26, wherein the cobalt source comprises cobalt acetate,cobalt napthenate, cobalt sulfate, cobalt acetylacetonate, cobaltbenzoylacetonate, cobalt bromide, cobalt carbonate, cobalt chloride,cobalt fluoride, cobalt nitrate, cobalt stearate, or a hydrate of one ofthe foregoing cobalt compounds.
 28. The method of claim 27, wherein thecobalt source comprises cobalt acetate or a hydrate of cobalt acetate.29. The method of claim 26, wherein the manganese source comprisesmanganese acetate, manganese sulfate, manganese acetylacetonate,manganese bromide, manganese carbonate, manganese chloride, manganesefluoride, manganese nitrate, or a hydrate of one of the foregoingmanganese compounds.
 30. The method of claim 29, wherein the manganesesource of comprises manganese acetate or a hydrate of one of theforegoing manganese compounds.
 31. The method of claim 26, wherein thesource of zirconium comprises zirconium acetate, zirconium sulfate,zirconium citrate, zirconium fluoride, zirconium hydroxide, zirconiumalkoxide, zirconium chloride, zirconium bromide, zirconiumacetylacetonate, or a hydrate of one of the foregoing zirconiumcompounds.
 32. The method of claim 31, wherein the source of zirconiumcomprises zirconium acetate or a hydrate of zirconium acetate.
 33. Themethod of claim 26, wherein the source of hafnium comprises hafniumchloride, hafnium bromide, hafnium fluoride, hafnium iodide, hafniumnitride, hafnium sulfate, hafnium triflate, hafnium nitrate, or ahydrate of one of the foregoing hafnium compounds.
 34. The method ofclaim 33, wherein the source of hafnium comprises hafnium chloride. 35.The method of claim 26, wherein the source of bromide comprises bromine,hydrogen bromide, a metal-bromide salt or an organic bromide.
 36. Themethod of claim 35, wherein the source of bromide comprises sodiumbromide.
 37. The method of claim 35, wherein the source of bromidecomprises hydrogen bromide.
 38. The method of claim 23, wherein theamount of the cobalt source is about 0.5 to about 1.2 mole percent,based on said chloro-ortho-xylene.
 39. The method of claim 23, whereinthe amount of the manganese source is about 0.3 to about 0.6 molepercent, based on said chloro-ortho-xylene.
 40. The method of claim 23,wherein the amount of the source of zirconium or hafnium is about 0.03to about 0.06 mole percent, based on said chloro-ortho-xylene.
 41. Themethod of claim 23, wherein the amount of the source of bromide is lessthan or equal to about 0.04 mole percent, based on saidchloro-ortho-xylene.
 42. The method of claim 23, wherein the amount ofthe source of bromide is less than or equal to about 0.03 mole percent,based on said chloro-ortho-xylene.
 43. The method of claim 23, whereinthe temperature is greater than or equal to 160° C.
 44. The method ofclaim 23, wherein the conversion of said chloro-ortho-xylene tochlorophthalic acid is 95 percent or greater.
 45. The method of claim23, wherein said chloro-ortho-xylene comprises the 3-isomer, the4-isomer or a mixture of 3- and 4-isomers.
 46. The method of claim 23,wherein said acetic acid is recycled to the reaction mixture.
 47. Amethod for the manufacture of halophthalic acid comprising: forming areaction mixture comprising: a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.8 to about 1.2 mole percent, based on said halo-ortho-xylene, of acobalt source, about 0.4 to about 0.6 mole percent, based on saidhalo-ortho-xylene, of a source of manganese, about 0.04 to about 0.06mole percent, based on said halo-ortho-xylene, of a source of a metalselected from zirconium, hafnium and mixtures thereof, less than about0.04 mole percent, based on said halo-ortho-xylene, of a bromide source;maintaining said reaction mixture at a pressure of at least about 1600Kpa and at a temperature of about 130° C. to about 200° C.; introducinga molecular oxygen containing gas to said reaction mixture at a rate ofat least about 0.5 normal m³ of gas/kg of halo-ortho-xylene in saidreaction mixture for a time sufficient to provide at least about 90percent conversion of said halo-ortho-xylene to halophthalic acid.
 48. Amethod for the manufacture of halophthalic anhydride comprising: forminga reaction mixture comprising: a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.8 to about 1.2 mole percent, based on said halo-ortho-xylene, ofcobalt acetate or cobalt acetate hydrate, about 0.4 to about 0.6 molepercent, based on said halo-ortho-xylene, of manganese acetate ormanganese acetate hydrate, about 0.04 to about 0.06 mole percent, basedon said halo-ortho-xylene, of zirconium acetate or zirconium acetatehydrate, less than about 0.04 mole percent, based on saidhalo-ortho-xylene, of sodium bromide; maintaining said reaction mixtureat a pressure of at least about 1600 Kpa and at a temperature of about130° C. to about 200° C.; introducing a molecular oxygen containing gasto said reaction mixture at a rate of at least about 0.5 normal m³ ofgas/kg of halo-ortho-xylene in said reaction mixture for a timesufficient to provide at least about 90 percent conversion of saidhalo-ortho-xylene to halophthalic acid; removing the acetic acid and anywater formed as a result of the reaction by distillation; separatingsaid water from said acetic acid and recycling said acetic acid;dehydrating said halophthalic acid to form halophthalic anhydride.
 49. Amethod for the manufacture of polyetherimide comprising: forming areaction mixture comprising: a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.25 to about 2 mole percent, based on said halo-ortho-xylene, of acobalt source, about 0.1 to about 1 mole percent, based on saidhalo-ortho-xylene, of a manganese source, about 0.01 to about 0.1 molepercent, based on said halo-ortho-xylene, of a source of a metalselected from zirconium, hafnium and mixtures thereof, about 0.02 toabout 0.1 mole percent, based on said halo-ortho-xylene, of a bromidesource; maintaining said reaction mixture at a pressure of at leastabout 1600 KPa and at a temperature of about 130° C. to about 200° C.;introducing a molecular oxygen containing gas to said reaction mixtureat a rate of at least about 0.5 normal m³ of gas/kg of halo-ortho-xylenein said reaction mixture for a time sufficient to provide at least about90 percent conversion of said halo-ortho-xylene to halophthalic acidwith less than about 600 parts per million (ppm) of halophthalide;maintaining the resultant reaction mixture at 200° C. under reducedpressure to remove, as a vapor, said acetic acid and any water formed asa result of the reaction; dehydrating said halophthalic acid to formhalophthalic anhydride; reacting said halophthalic anhydride with1,3-diaminobenzene to form bis (halophthalimide) (II)

wherein X is a halogen; and reacting bis(halophthalimide) (II) with analkali metal salt of a dihydroxy substituted aromatic hydrocarbon havingthe formula (IV) OH—A²OH  (IV) wherein A² is a divalent aromatichydrocarbon radical to form the polyetherimide.